2024-04-07 22:00:00
Will there soon be an end to stool exams and colonoscopies (colonoscopies)? A promising study shows that early stage colon cancer could be detected in 83% of cases based on a simple blood test. How is it possible ?
See also the article: Colorectal cancer (colon cancer)
How does colon cancer develop?
Colorectal cancer is a cancer that most often develops from polyps that form on the lining of the colon or rectum. Most of these growths are benign. But in some cases, they slowly (over 5 to 10 years) transform into a cancerous tumor. These polyps do not cause visible symptoms (to the naked eye). Screening is therefore crucial in order to detect and remove them before the appearance of colon cancer.
See also the article: From polyps to colon cancer: the importance of screening
How is colon cancer detected today?
Today, in Belgium, colorectal cancer screening is carried out on the basis of a stool sample taken every two years between the ages of 50 and 74. If the sample shows traces of occult blood (blood invisible to the naked eye), this may be a sign that a polyp or cancerous tumor is bleeding. If you test positive, you will need to perform a colonoscopy (colonoscopy) so that the lesions can be visualized and removed.
See also the article: Blood in the stool: the causes and when to worry
Traces of colon cancer in the blood
According to a study published in The New England Journal of Medicine, a blood test could detect DNA fragments likely to be released by colon tumors into the bloodstream (circulating tumor DNA or ctDNA). This cell-free DNA (cfDNA) test is believed to be able to detect colorectal cancer at early, treatable stages.
The study was carried out on the basis of a sample of 7,861 people aged 45 to 84 years. The results of the blood tests were compared to those of the colonoscopies. 83.1% of participants with colorectal cancer confirmed by colonoscopy had a positive blood test for ctDNA and 16.9% had a negative test even though colonoscopy had nevertheless diagnosed cancer.
For one of the study’s authors, gastroenterologist William M. Grady, “the study results represent a promising step toward developing more practical tools to detect colorectal cancer at an early, treatable stage.” . The test could offer an alternative to patients who refuse current screening options.”
The limits of the blood test as a screen for colon cancer
However, research has not shown satisfactory results in detecting polyps or advanced precancerous lesions. The test only detected it in 13% of cases, compared to 42% during stool analysis and 93% through colonoscopy.
The test would therefore make it possible to treat cancer at an early stage, but not to prevent its appearance by detecting polyps before they develop into their cancerous form.
For Dr. William M. Grady, however, the blood test remains an asset: “colorectal cancer is common and can be avoided through screening, but within certain populations, less than half of those eligible for screening actually undergo screening. these tests… The possibility of carrying out a blood test during routine visits to the doctor could be an opportunity to help more patients get screened. »
“We continue to see younger people suffering from colorectal cancer and it is now the third most common cancer in people under 50.”
See also the article: Cancer: a blood test detects a large number of cancers before the first symptoms
Sources :
Last updated: April 2024
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